Open access is a movement that seeks to make scholarly materials such as published and unpublished articles, manuscripts, and datasets available to the public in a way that they never have been before.
Open access literature is usually defined as "digital, online, free of charge, and free of most copyright and licensing restrictions" and "is entirely compatible with peer review" (Suber, 2008).
It is made possible by the distribution power of the Internet and the consent of the author or copyright-holder (Suber, 2008).
Open access materials are reported to be downloaded more than traditionally published materials (Davis et al, 2008), to provide more opportunities for easier collaboration among researchers, and are even cited more than restricted (non-open access) materials in some disciplines (Lawrence, 2001).
This short animated video explains open access to research and why it is important.
Open Access 101, from SPARC from Karen Rustad on Vimeo.
Citation Advantage of Open Access Scholarship
Study concludes: "Open access legal scholarship... can expect to receive 58% more citations than non-open access writings of similar age from the same venue."
Scholars find high quality work that gets cited often
Whether a college or university mandates a scholar to put his or her work in a publicly accessible Website, or the scholar is free to self archive as little or as much as he or she desires, the open access work is often cited, according to this article from PLoS ONE, an open access science journal.